Sending over UDP


i want to send strings to a PC that is connected to the IRC5.
Its a IRB2600 with PC-Interface option. 
The PC is connected to the wan port an the Robot. Were using a tool that is listening to the ip of the robot to write the strings in .txt files ( its just for logging what the robot is doing ).
We tested the programm with a simulated station on my laptop, and the laptop was connected to another PC with the running tool. This works fine.
So we tested the programm on the Robot. But the tool didnt receive any strings.
I think it didnt work because the Robot is sending the UDP over the different IP/port but i cant set the port the Robot is using.
The Robot has connected IO on the Lan port, but the WAN port has a different ip.

Has someone a similiar problem? Or any idea why this dont work?